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DYNAMICS OF WING CRACKS AND NANOSCALE DAMAGE IN SILICA GLASS
by
Zhen Lu
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MATERIAL SCIENCE)
December 2007
Copyright 2007 Zhen Lu

Multimillion atom molecular-dynamics (MD) simulations were performed to investigate dynamic fracture in silica glasses. Simulations identified the atomistic mechanisms for the nucleation, growth, and healing of wing cracks in a confined precracked glass. Under dynamic compression, frictional sliding of pre-crack surfaces nucleates nanovoids which evolve into nanocrack columns at the pre-crack tip. Nanocrack columns merge to form a wing crack, which grows via coalescence with nanovoids in the direction of maximum compression. The main growth mechanism of the wing crack is shown to be damage induced by the disorder intrinsic to the amorphous structure. Lateral confinement arrests the growth and partially heals the wing crack. Growth and arrest of the wing crack occur repeatedly, as observed in dynamic compression experiments on brittle solids under lateral confinement.

DYNAMICS OF WING CRACKS AND NANOSCALE DAMAGE IN SILICA GLASS
by
Zhen Lu
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(MATERIAL SCIENCE)
December 2007
Copyright 2007 Zhen Lu